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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Syntax Definition Formalism | 1/1 | https://en.wikipedia.org/wiki/Syntax_Definition_Formalism | reference | science, encyclopedia | 2026-05-05T11:39:36.670441+00:00 | kb-cron |
The Syntax Definition Formalism (SDF) is a metasyntax used to define context-free grammars: that is, a formal way to describe formal languages. It can express the entire range of context-free grammars. Its current version is SDF3. A parser and parser generator for SDF specifications are provided as part of the free ASF+SDF Meta Environment. These operate using the SGLR (Scannerless GLR parser). An SDF parser outputs parse trees or, in the case of ambiguities, parse forests.
== Overview == Features of SDF:
Supports the entire range of context-free languages Allows modular syntax definitions (grammars can import subgrammars) which enables reuse Supports annotations
== Examples == The following example defines a simple Boolean expression syntax in SDF2:
module basic/Booleans
exports sorts Boolean context-free start-symbols Boolean
context-free syntax
"true" -> Boolean
"false" -> Boolean
lhs:Boolean "|" rhs:Boolean -> Boolean {left}
lhs:Boolean "&" rhs:Boolean -> Boolean {left}
"not" "(" Boolean ")" -> Boolean
"(" Boolean ")" -> Boolean
context-free priorities Boolean "&" Boolean -> Boolean > Boolean "|" Boolean -> Boolean
== Program analysis and transformation systems using SDF == ASF+SDF Meta Environment provides SDF RascalMPL Spoofax/IMP [1] Stratego/XT Strafunski
== See also == GNU bison ANTLR
== References ==
== Further reading == A Quick Introduction to SDF, Visser, J. & Scheerder, J. (2000) CWI The Syntax Definition Formalism SDF, Mark van den Brand, Paul Klint, Jurgen Vinju (2007) CWI
== External links == Grammar Deployment Kit SdfMetz computes metrics for SDF grammars Download SDF from the ASF+SDF Meta Environment homepage